During the production of synthetic yarns, separate filaments are formed from a thermoplastic, such as e.g. polypropylene, polyester or polyamide. This is achieved using an extrusion process. A number of these filaments are combined to form a so-called multifilament yarn. It is known to improve the properties of a multifilament yarn by texturation in order to improve its suitability for certain applications. This is done, for example by bringing a heated gaseous medium, such as hot air, near the filaments in a texturing channel at high speed. As a result thereof, the filaments are moved into the texturing channel and are deformed in a part of the texturing channel that is situated further away. Subsequently, the yarn is set, thus producing a crimped yarn. As a result hereof, the yarn is more voluminous and acquires a better covering capacity which is certainly advantageous for synthetic yarns which are used to weave or to tuft carpets.
Known texturing devices, such as the device described in U.S. Pat. No. 6,309,388 B 1, comprise a texturing unit in which two texturing channels are provided parallel to each other. A respective multifilament yarn is introduced into each channel via an inlet opening in the channel. An air inlet is provided in each channel via which hot air is blown into the texturing duct at great speed. This air has a temperature which is sufficiently high to bring the plastic material up to a processing temperature at which the plastic is weak and deforms easily. In a well-defined zone, the texturing channels are made wider and provided with outlet openings via which air can escape. The yarn is carried along by the hot air into the texturing channels. In the wider zones of these channels, the speed of the air and the yarn drops significantly, as a result of which the yarn is compressed to form a yarn plug, and is moved in the channel as a yarn plug and eventually leaves the texturing channel via a discharge opening. Subsequently, the two yarn plugs are placed on the lateral surface of a slowly rotating cooling drum in order to cool. The deformations of the filaments are thus set. The textured yarn is then lead away from the surface of the cooling drum and subjected to any additional treatments and is finally wound onto bobbins as a crimped textile yarn.
The properties of such a textured yarn are inter alia determined by the circumstances in which the yarn cools after having completed the texturing process. In the known texturing devices, the yarn plugs are taken to a cooling surface via relatively long separate channels after leaving the two adjacent texturing channels. As a result thereof, the circumstances in which these yarn plugs cool on their path between the texturing channel and the cooling surface may differ to the degree that the simultaneously textured yarns have mutually different properties.